In the future, improving the quality of cardiac coronary system visualization will allow for better planning of cardiac interventional procedures and, therefore, decreased patient risk [1]. Note, that several visualization modalities are currently employed and continue to be developed so to enhance visualization of the coronary system: see following.
Angiography
Catheterization of the heart is a somewhat invasive but commonly employed procedure for visualization of the heart's coronary vessels, chambers, valves, and/or great vessels. Basic catheterization techniques involve inserting a long, flexible, radio-opaque catheter into either a peripheral vein (for venous or right heart catheterization) or peripheral artery (for coronary artery or the left heart) under fluoroscopy (continuous X-ray observation). During this invasive procedure, a radio-opaque contrast medium is commonly injected into a cardiac vessel or chamber. Thus, this type of procedure may be used to visualize the anatomical features of the coronary arteries, cardiac veins, aorta, pulmonary blood vessels, and/or ventricles. Such investigations may provide pertinent clinical information about structural abnormalities in blood vessels that restrict flow (such as those caused by atherosclerotic plaque), abnormal ventricular blood volumes, inappropriate myocardial wall thicknesses, and/or altered wall motions. However, it should be noted that multiple contrast injections can be potentially acutely deleterious to patients, especially in those with compromised cardiac outputs [2].
To date, coronary artery angiography has been the primary visualization modality used clinically. Contrast is injected into the coronary arteries to identify existing occlusions or narrowing due to atherosclerotic plaques/calcifications. This visualization approach also provides the physician with roadmaps for the delivery of percutaneous therapies (e.g., a coronary stent) or for planning a subsequent coronary artery bypass surgery (i.e., determine where best to place suture so to avoid an attempted assess to a rigid calcified arterial wall) [3].
A sample venogram from an isolated heart preparation can be seen to the right. The green sheath contains a venogram balloon catheter. The balloon is inflated to block off antegrade flow and then contrast is injected retrograde, such that the coronary venous system (branching) is visible. Such imaging techniques are typically used for mapping the target vein for the delivery of a left-sided pacing lead (e.g., for biventricular pacing therapies). For more examples of angiography, please see the Venograms section of the Atlas.
Movie showing a venogram in an isolated heart. The movie shows a catheter cannulating the coronary sinus ostium, then switches to a fluoroscopic
view of the heart, where the coronary veins become opaque as a contrast agent is injected.
Computed Tomography (CT)
Electron beam computed tomographic (CT) angiography allows minimally invasive, detailed visualization of the coronary system [4]. More specifically, multi-slice computed tomography uses a 4-dimensional functional imaging computed tomography scanner, thus to obtain structural and functional features. Obtained, high quality, virtual images show details such that transvenous lead implantation, for instance, can be better planned so to reduce both procedure times and patient risks [1].
Our lab has been obtaining computed tomography images of isolated perfusion fixed hearts with contrast injected into the coronary vasculature systems [5,6,7,8]. From these scans we have generated three-dimensional models of both the cardiac veins and coronary arteries. Additionally, we have created and continue to develop a database of anatomical parameters measured from these models: e.g., which than can be used for the design of medical devices that are to be deployed within the coronary vessels.
Ultrasound
Various types of ultrasound are also used to visualize the coronary system. For instance, prior to lead implantation, tissue Doppler imaging can be utilized to identify the target implant region for a transvenous pacing lead placements [9]. Additionally, intravascular ultrasound (IVUS) can be used to identify the presence or absence of calcifications within the coronary arteries: e.g., during a procedure for the delivery of stents.
Optical Coherence Tomography
Another current intravascular visualization method is Optical coherence tomography (OCT). OCT generates infrared light and processes the reflections into in-vivo images that can be used in the verification of implanted stents [10,11]. OCT provides higher image resolution than IVUS, but more limited penetration in the vasculature [10,11].
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Spencer, J., Fitch, E., & Iaizzo, P. A. (2013). Anatomical reconstructions of the human cardiac venous system using contrast-computed tomography of perfusion-fixed specimens. JoVE (Journal of Visualized Experiments), (74), e50258-e50258
Spencer, Julianne H., et al. "A detailed assessment of the human coronary venous system using contrast computed tomography of perfusion-fixed specimens." Heart Rhythm 11.2 (2014): 282-288
Spencer, J. H., Sundaram, C. C., & Iaizzo, P. A. (2014). The relative anatomy of the coronary arterial and venous systems. Clinical Anatomy
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Puri R, Worthley M, Nicholls S (2011) Intravescular imaging of vulnerable coronary plaque, current and future concepts. Nature Rev 8:131-139
Bezerra H, Costa M, Guagliumi G, Rollins A, Simon D (2009) Intracoronary optical coherence tomography, a comprehensive review clinical and research applications. JACC Cardiovasc Interv 2:1035-1046
